In situ monitoring of electrophoretic deposition of Cu2ZnSnS4 nanocrystals

Cu2ZnSnS4 (CZTS) nanocrystal (NC) layers were deposited successfully by electrophoretic deposition (EPD) on molybdenum and fluorine doped tin oxide coated glass substrates. This approach combines a non-vacuum coating technique known for its industrial eligibility to a solar absorber material consisting solely of non-toxic and earth abundant elements. CZTS NC layers with thicknesses between 200 nm and 1.5 μm were formed in 0.5 to 1 min while the NC dispersion, consisting of organic solvents, depleted entirely. Therefore the layer thickness can be controlled by varying the concentration of NCs in dispersion. Scanning electron microscopy micrographs show compact and homogeneous films. The layers were analyzed by grazing incidence X-ray diffraction, Raman analysis. Optical properties were probed by UV-vis spectroscopy. The dependence of dispersion composition and applied voltage on deposition dynamics and duration was analyzed by the use of an optical monitoring setup. The results open up a route of low cost CZTS thin film fabrication with reduced chemical contamination, fast layer deposition and high raw material use

Enhanced urban adaptation efforts needed to counter rising extreme rainfall risks

Record-breaking rainfall events are occurring more frequently in a warming climate. Impacts on lives and livelihoods disproportionately occur in traditionally underserved communities, particularly in urban areas. To influence policy and behavioral change at the community level, climate services must be developed specific to extreme rainfall events and subsequent floods in urban environments

The day the 2003 European heatwave record was broken

On June 28, 2019, a temperature of 45·9°C was recorded at a weather station in France, exceeding the country's previous temperature record—set during the infamous 2003 heatwave—by almost 2°C. The heatwave peaked over central and northern Europe, fuelled by a very persistent planetary-scale Rossby wave (giant meanders in upper-tropospheric winds), which turned into an omega block, so named because its shape resembles the Greek letter (Ω). This blocking event led to hot air from northern Africa being transferred to Europe. Given the extraordinary nature of this event, the public and media are now wondering: is such weather the new norm, and how bad could it get in the future

The Disruption of Arctic Exceptionalism: Managing Environmental Change in Light of Russian Aggression

The Arctic is directly affected by the interaction of two ongoing global crises: climate change and Russia's war of aggression against Ukraine. With its temperatures rising four times faster than the global average, the Arctic is facing dramatic environmental consequences. Meanwhile, retreating sea ice has led to increased economic interest in the Arctic and its growing geopolitical importance. Thus, understanding and managing the global and local implications of environmental change in this region requires urgent scientific and diplomatic collaboration

Synthesis of Cu2ZnxSnySe1+x+2y nanocrystals with wurtzite-derived structure

The most reported stable crystal structure of Cu2ZnSnS4 and Cu2ZnSnSe4 (CZTSe) is kesterite, which is derived from the ternary chalcopyrite structure. However, by controlling the reaction conditions, we found that the structure and composition of the CZTSe nanocrystals (NCs) can be tuned. This can be achieved by using a simple hot injection approach. The structural properties of the CZTSe NCs were characterized by powder X-ray diffraction (PXRD), Raman spectroscopy and transmission electron microscopy. The energy dispersive X-ray spectroscopy confirms the stoichiometry of CZTSe NCs. The optical band gap of the NCs is found to be around 1.38 eV, as estimated from UV-Vis absorption spectroscopy. PXRD studies show that the obtained CZTSe NCs occurring in three structurally different phases (tetragonal kesterite type, hexagonal wurtzite type and orthorhombic wurtz-stannite type) are converted to the kesterite structure by annealing at 540 °C for 30 min under an Se-vapour atmosphere

Cu2ZnSn(S,Se)4 from CuxSnSy nanoparticle precursors on ZnO nanorod arrays

Solar cells with Cu2ZnSnS4 absorber thin films have a potential for high energy conversion efficiencies with earth-abundant and non-toxic elements. In this work the formation of CZTSSe from CuxSnSy nanoparticles (NPs) deposited on ZnO nanorod (NR) arrays as precursors for zinc is investigated. The NPs are prepared using a chemical route and are dispersed in toluene. The ZnO NRs are grown on fluorine doped SnO2 coated glass substrates by electro deposition method. A series of samples are annealed at different temperatures between 300 °C and 550 °C in selenium containing argon atmosphere. To investigate the products of the reaction between the precursors the series is analyzed by means of X-ray diffraction (XRD) and Raman spectroscopy. The morphology is recorded by scanning electron microscopy (SEM) images of broken cross sections. The XRD measurements and the SEM images show the disappearing of ZnO NRs with increasing annealing temperature. Simultaneously the XRD and Raman measurements show the formation of CZTSSe. The formation of secondary phases and the optimum conditions for the preparation of CZTSSe is discusse

Assessing changes in risk of amplified planetary waves in a warming world

Summer weather extremes are often associated with high‐amplitude atmospheric planetary waves (Petoukhov et al., 2013). Such conditions lead to stationary weather patterns, triggering heat waves and sometimes prolonged intense rainfall. These wave events, referred to as periods of Quasi‐Resonant Amplification (QRA), are relatively rare though and hence provide only a few data points in the meteorological record to analyse. Here, we use atmospheric models coupled to boundary conditions that have evolved slowly (i.e., climate), to supplement measurements. Specifically we assess altered probabilities of resonant episodes by employing a unique massive ensemble of atmosphere‐only climate simulations to populate statistical distributions of event occurrence. We focus on amplified waves during the two most extreme European heat waves on record, in years 2003 and 2015 (Russo et al., 2015). These years are compared with other modelled recent years (1987–2011), and critically against a modelled world without climate change. We find that there are differences in the statistical characteristics of wave event likelihood between years, suggesting a strong dependence on the known and prescribed Sea Surface Temperature (SST) patterns. The differences are larger than those projected to have occurred under climate change since the pre‐industrial period. However, this feature of small differences since pre‐industrial is based on single large ensembles, with members consisting of a range of estimates of SST adjustment from pre‐industrial to present. Such SST changes are from projections by a set of coupled atmosphere–ocean (AOGCM) climate models. When instead an ensemble for pre‐industrial estimates is subdivided into simulations according to which AOGCM the SST changes are based on, we find differences in QRA occurrence. These differences suggest that to reliably estimate changes to extremes associated with altered amplification of planetary waves, and under future raised greenhouse gas concentrations, likely requires reductions in any spread of future modelled SST patterns

Compound Climate Events and Extremes in the Midlatitudes: Dynamics, Simulation, and Statistical Characterization

The workshop, conducted virtually due to travel restrictions related to COVID-19, gathered scientists from six countries and focused on the mechanistic understanding, statistical characterization, and modeling of societally relevant compound climate events and extremes in the midlatitudes. These ranged from co-occurring hot–humid or wet–windy extremes, to spatially compounding wet and dry extremes, to temporally compounding hot–wet events and more. The aim was to bring together selected experts studying a diverse range of compound climate events and extremes to present their ongoing work and outline challenges and future developments in this societally relevant field of research

Recent Increases in Exposure to Extreme Humid-Heat Events Disproportionately Affect Populated Regions

Extreme heat research has largely focused on dry-heat, while humid-heat that poses a substantial threat to human-health remains relatively understudied. Using hourly high-resolution ERA5 reanalysis and HadISD station data, we provide the first spatially comprehensive, global-scale characterization of the magnitude, seasonal timing, and frequency of dry- and wet-bulb temperature extremes and their trends. While the peak dry- and humid-heat extreme occurrences often coincide, their timing differs in climatologically wet regions. Since 1979, dry- and humid-heat extremes have become more frequent over most land regions, with the greatest increases in the tropics and Arctic. Humid-heat extremes have increased disproportionately over populated regions (∼5.0 days per-person per-decade) relative to global land-areas (∼3.6 days per-unit-land-area per-decade) and population exposure to humidheat has increased at a faster rate than to dry-heat. Our study highlights the need for a multivariate approach to understand and mitigate future harm from heat stress in a warming world

Neurogranin and YKL-40: independent markers of synaptic degeneration and neuroinflammation in Alzheimer’s disease

Introduction Neuroinflammation and synaptic degeneration are major neuropathological hallmarks in Alzheimer’s disease (AD). Neurogranin and YKL-40 in cerebrospinal fluid (CSF) are newly discovered markers indicating synaptic damage and microglial activation, respectively. Methods CSF samples from 95 individuals including 39 patients with AD dementia (AD-D), 13 with mild cognitive impairment (MCI) due to AD (MCI-AD), 29 with MCI not due to AD (MCI-o) and 14 patients with non-AD dementias (non-AD-D) were analyzed for neurogranin and YKL-40. Results Patients with dementia or MCI due to AD showed elevated levels of CSF neurogranin (p < 0.001 for AD-D and p < 0.05 for MCI-AD) and YKL-40 (p < 0.05 for AD-D and p = 0.15 for MCI-AD) compared to mildly cognitively impaired subjects not diagnosed with AD. CSF levels of neurogranin and YKL-40 did not differ between MCI not due to AD and non-AD dementias. In AD subjects no correlation between YKL-40 and neurogranin was found. The CSF neurogranin levels correlated moderately with tau and p-tau but not with Aβ42 or the MMSE in AD samples. No relevant associations between YKL-40 and MMSE or the core AD biomarkers, Aβ42, t-tau and p-tau were found in AD subjects. Conclusions Neurogranin and YKL-40 are promising AD biomarkers, independent of and complementary to the established core AD biomarkers, reflecting additional pathological changes in the course of AD